Connectors for PV cells are usually supplied wound as long ribbons on rolls and are then cut off individually from these ribbons. The definition of the first and second broad side or the top and bottom is governed by the winding in the finished supplied form and can to this extent be as desired. In the present description, the first broad side or top is designated the side facing the incoming sunlight (so-called “sunny side”).
Connectors are used in photovoltaics in order to connect the individual PV cells to a PV module. Five PV cells for example are series-connected by means of the connectors. Each connector creates the electrical connection between two consecutive cells of a PV module. As a rule the connectors are used with PV cells of crystallized silicon. However, they can also be used in thin-film PV cells. The connectors are to securely join together the electric poles (positive and negative) of adjacent cells within the PV module, corresponding to the desired connection. As the PV cells are connected in series (positive to negative) and the orientation of the poles of each cell is the same, the connector is soldered to the top (so-called “sunny side”) of one cell and then to the bottom (so-called “shady side”) of the next cell.
Conventional connectors of PV cells are strips of electrically conductive material, generally copper, wherein both broad sides are smooth. Depending on the production method, the strip is pre-tinned with a soft solder on all sides (dip-tinned rolled wire) or on two sides (slit ribbon). The solder coating is applied evenly along the entire length of the connector, generally evenly in the same thickness on both sides. The crosswise thickness distribution of the tin layer may vary depending on the production method. In the case of dip-tinned wire a lens forms. With the cut ribbon the thickness of the solder layer remains constant over the width.
PV cell connectors with a corrugated structure are known from the publication “OPTIMISATION OF CELL INTERCONNECTORS FOR PV MODULE PERFORMANCE ENHANCEMENT”, 14th EUROPEAN PHOTOVOLTAIC SOLAR ENERGY CONFERENCE, BARCELONA, SPAIN, 30 Jun. to 4 Jul. 1997, as well as from US-2007/0125415 A1 and from JP 2006-013406. As described in these publications, with an optimum angle at the peaks of the corrugated structure of 100-140°, preferably 120°, approximately 80% of the light striking the connectors can be made usable for electricity generation by total reflection within the PV cell, whereby the overall efficiency of the PV cell is improved by approximately 2%. The surface of the corrugated structure can be silver-plated to increase the reflection. It is not stated in these published documents how the connectors are to be soldered to the PV cells. Conventional connectors with flat broad sides are pre-tinned by dip soldering. With connectors with a corrugated structure this does not lead to an adequate pre-tinning which allows the connectors to be soldered in an automated procedure. Connectors with a corrugated structure could therefore be soldered onto PV cells only by external solder feed, e.g. by means of a dispensing head.
Therefore there is a need to create a connector with a corrugated structure on at least one of the two broad sides which can be easily and reliably soldered to PV cells, as well as a method for producing such PV cell connectors.